How to represent class instances in UML?

Question

I have a class diagram for my application which consists of several compositions and aggregations.

Now I want to have diagram based on the class diagram which shows class instances. A snapshot if you will. I need this because it would help discussing some functional requirements.

Class diagram:

 --------   1                 *  ------- 
| Parent |----------------------| Child |
 --------                        -------

"Instance" diagram:

 --------                        --------- 
| Parent |----------------------| Child 1 |
 --------           |            ---------
                    |
                    |            ---------
                    +-----------| Child 2 |
                    |            ---------
                    |
                    |            ---------
                    +-----------| Child 3 |
                                 ---------

Is there a diagram type for this? (Currently I'm mis-using a class diagram, where all my instances are separate classes)

Bandeen

Answer 1

• Use Object diagram or
• Use keyword <<instance>> or
• Underline class name

Sophrosyne

Object diagram likely most appropriate as, from original q, an objective is to illustrate relationship cardinality. – Sites

Unfortunately the last two links are dead. – Coating

web.archive.org/web/20140523210656/http://hcs.science.uva.nl/… – Sophrosyne

Answer 2

An "instance" diagram in UML is called an Object Diagram.

Emblazonry

Answer 3

You can use the "Object Diagram" as Peter G. McDonald said.

See the wiki :Object Diagram Wiki
In UML if what you want doesn't exist you can adapt classic Diagram for what you want
something just like you did but with comment block to explain your choices
Documentation is as important as diagrams.

If you want to describe the life cycle of yours instances you can use "State machine diagram".

Prisage